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CHAPTER 2: NUTRITION1. Living things need food to survive.
2. Food can divided into seven classes as
follows:
i. carbohydrates
ii. proteins
iii. fats
iv. vitamins
v. minerals
vi. fibre
vii. water
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Carbohydrate
1. Carbohydrate is made up of carbon, hydrogen
and oxygen.2. There are three types of carbohydrate, starch,
sugar and cellulose.
3. Carbohydrate are present in various forms,such as:
i. starch, which is stored in plants.(bread,
potatoes)ii. Sugars, which are sweet and soluble in water.
iii. Cellulose, which is found in plant cell walls
and cannot bedigested.(vegetable and fruits)
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iv. Glycogen, which is found in liver and muscles.4. Food rich in carbohydrate include rice;
potato, sugar, bread, and banana.
5. Carbohydrate is our main source of energy.Carbohydrate supplies us with
energy to carry out daily activities such as
walking, breathing, andworking.
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Protein1. Protein is made up of carbon, hydrogen,
oxygen, and nitrogen.
2. Sometimes protein can also containphosphorus and sulphur.
3. Food rich in protein includes fish, milk, meat,
egg white and nuts(groundnuts and soya bean).
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4.Proteins are required for building new cells forgrowth, to replace
damaged tissue.
5. Growing children require a lot of protein.
Lack of protein will cause a
disease know as kwashiorkor (stunted growth).
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Fat
1. Fat is made up for carbon, hydrogen and
oxygen but the ratio is different
from that of carbohydrate.
2. Food rich in fats includes palm oil, butter and
egg yolk.
3. Fat produces twice the amount of energy
compared with carbohydrate of
the same weight.
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4. The function of fat include:a. supplying energy,
b. as and insulator of heat to reduce heat loss
from the body,c. protecting the internal organs such as the
kidneys and the heart,
d. dissolving some vitamins in the body likevitamin A, D, E and K.
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Vitamins
1. Vitamins are required in small quantities only.
2. Vitamins are classified into two groups
a. vitamins soluble in water vitamin B and C ,
b. vitamins soluble in fat- vitamin A, D, E and K.
3. Vitamins protect the body from various types
of diseases and maintains the
health of the body.
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Vitamin Main source Function Effect of
deficiency
AEgg, milk, cod
liver,
oil, carrot,papaya
-for growth
and to
promotehealthy skin
- for good
vision
- night
blindness
- dry andscaly skin
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Byeast, egg,
milk,
tomato,liver, nuts
- promotes
the effective
functioningof the
nervous
system- control the
supply of
carbohydrates to the
muscle and
nerve cells
- beri-beri
(injury to
thenervous
system
andparalysis)
- pellagra
- anaemia
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Clime, citrus
fruits,
tomato,carrot ,
papaya,
greenvegetables
- increase
immunity
againstdisease
- promotes
healthy skin
scurvy
(gusi
merah)- anaemia
- low
resistanceto
infections
(especiallythe flu)
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Degg, milk, cod
liver oil
helps in the
absorption of
calcium and
phosphorus
in the
small
intestines forthe growth
of strong
bones andteeth.
- rickets
(weak and
curvedbones)
- tooth
decay
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E
K
vegetable
oil, palm oil,
egg, liver,milk
maize,
sunflower
seeds,tomato,
green
vegetables
- maintains a
healthy
reproductivesystem
- necessary
for the
clotting ofblood.
sterility
Infertility
blood
slow to
clot
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Minerals
1. minerals are simple chemicals usually found
in the body.2. our bodies need more calcium and
phosphorus than the minerals.(because
they help to form strong bones and teeth)3. minerals are needed for good health.
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sources of
food
Functions effects of
deficiency
Calcium milk, eggs,
Vegetable,cheese
* forms
strongbones
and teeth
* helpsblood to
colt
* rickets
* brittlebones and
teeth
* poorblood
clotting
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sources of
food
Functions effects of
deficiency
iron liver, meat,
eggs,vegetables
forms
haemoglobinin red the
thyroid
blood cells
anaemia
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sources of
food
Functions effects of
deficiency
iodine seafood,
vegetablesiodinised
salt
*produces
hormonesin the
thyroid
gland
* Goitre
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sources
of food
Functions effects of
deficiency
Sodium
phosphorus
common
salt,
meat,
milk,eggs,
beans
balances
body fluid
* forms
strongbones
and teeth
* muscle
cramps
* rickets
* dentaldecay
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sources of
food
Functions effects of
deficiency
Fluorine
potassium
drinking
water, fish,
Vegetables
meat, fish,
cereals
*protect
teeth
*maintains
ahealthy
nervous
system
* Dental
decay
muscle
cramps
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Fibre
1. Fibre is made up of cellulose which cannot be
digested by the body.
2. A shortage of fibre in our daily diet can cause
constipation and sometimes
even bowel cancer.
3. Vegetables, fruit, beans, lentils and brown
bread are examples of food
rich in fibre.
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Water1. approximately 65% to 70% of a persons body
weight is made up of water.
2. The body obtains water when we drink waterand also when we consume
fruits and vegetables.
3. Water is needed by the body for:a. helping in the digestion of food
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b. transporting digested food substances
c. transporting excretory products such as urea.
d. maintaining the concentration of blood.
e. maintaining the body temperature
f. all metabolic processes
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The importance of a balanced diet
1.Diet refers to the food and drinks that we consume
daily.
2. A balanced diet is one which contains
carbohydrates, proteins, fats,
minerals, vitamins, water and fibre in the correct
quantities and
proportions.
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3. A balanced diet is necessary for:
a. supplying the required energy
b. balanced body growthc. maintaining the health of the body
d. preventing deficiency diseases such as scurvy and
rickets.
4. A balanced diet varies according to ones
i. Age
ii. size
iii. sexiv. job
v. climate
vi. state of health
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Factors that influence a persons needs for
a balanced diet
sex
men required more energy compared to
women of the same age and body size.
men are more active.
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agebabies, children and teenagers require
more energy compared to adults or the
elderly.
Example: the heartbeat of baby
is 100 beats a minute compared to an
adult who has 75 beats per minute.
this group is more active and thelife processes are faster
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body size
big-size individuals require more energy
size compared to small-sized individuals.big-sized individuals require more
energy for their life processes.
Physical activity
an individual who does heavy work uses
more energy compared to another who
does light work.
heavy work requires more energy
to perform.
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weatherindividuals living in places with cold
weather require more energy compared to
individuals living in places with warmweather.
more energy is required to
maintain the body temperature in
a cold place.
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The calorific value of food
1. Energy in food measured in joules (J) or calories
(cal).
1 calorie (cal) = 4.2 joules (J)
1 kilocalorie (kcal) = 4.2 kilojoules (kJ)
2. The calorific value of food is the amount of heat
energy released whenone gram of food is completely burnt in the air.
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3. The calorific value of food is measured in kilojoulesper gram (kJ/g) or
kilocalories per gram (kcal/g)
4. The calorific value differs for different types of
food. Table below shows
the calorific value of some of the food that we eat
daily.
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food type calorific value (kJ/g)
margarine 35.5Cake 18.3
Rice 15.0
Roti canai 13.3
fried noodles 13.0
chicken curry 7.8
Egg 6.8
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Individual energy in kJ
child, 8 years old
male Femalechild, 8 years old 8800 8800
teenager, 15 years old 12600 9600
adult, clerk 11500 9450
adult, labourer 20000 12600
pregnant mother - 10000
lactating mother - 11300
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HUMAN DIGESTIVE SYSTEM
1. Digestion is the process of breaking down large and
complex food substances into smaller, simpler
molecules. These molecules are soluble and can beabsorbed by body cells.
2. the digestive process occurs in a system which is
called the digestive system.
3. Figure below shows the human digestive system
pg 49 figure 2.8 (Photostat)
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HUMAN DIGESTIVE SYSTEM
Digestion is the process of
___________________ food from a
__________ food molecules into ________
soluble molecules that can be readily
__________ by the ___________.
large breaking down
smaller body absorbed
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HUMAN DIGESTIVE SYSTEM
pg 49 figure 2.8 (Photostat)
LIVER
GALL BLADDER
STOMACH
DUODENUM
oesophagus
RECTUM
LARGEINTESTINE
SMALL INTESTINE
PANCREAS
ANUS
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parts of
the
digestivetract
Functions
Mouth chew and grinds food using the teeth
digests cooked starch. The amylaseenzymes in the saliva
change cooked starch to maltose.
The salivary glands secrete saliva which
contains an enzyme called amylase. Amylase digests starch and convert it to
maltose (a type of sugar)
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Oesophagus
bolus-shaped food is moved from the
mouth to the stomach
along the oesophagus by wave-likemuscular contractions called
peristalsis
Stomach
holds food, secretes gastric juices whichbegin the digestion of protein
secretes acids contains hydrochloric acid
which kill the bacteria in food.
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Duodenum
receives bile from the liver and
pancreatic juice from the pancreas.
Digestion and absorption of food.
small
intestine
secretes intestinal juice which completes
the digestion of protein, carbohydrates
and fat.Absorbs end products of digestion into
the blood.
large
intestine
absorption of most of the remaining
water and minerals
Rectum stores faeces
Anus removes faeces through defecation
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Match the foods to their respective functions.
Organ Function
Mouth o Digestion of protein starts here
Liver o Secretes pancreatic juice
Anus o Channels food to the stomach
Large intestine o Absorbs water from undigested food
Small intestine o Digests and absorbs food
Oesophagus o Removes the faeces from the body
Pancreas o Secretes bile to emulsify fats
Stomach o Cuts and chews the food
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6. The process of digestion in the alimentary canal:
a. physical digestion - involves the mechanical processof breaking down large pieces of food into smaller
particles using the teeth and the churning movements
of the alimentary canal.
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b. chemical digestion -involves the action of various
enzymes in breaking down complex food molecules.
These complex molecules are insoluble but the end
products of chemicals digestion are simpler molecules
which are soluble.
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Flow of food particles in the alimentary canal:
mouth
i. Digestion begins in the mouth.ii. The teeth chew and grind food into smaller
particles.
iii. the salivary glands secrete saliva which contains an
enzyme called amylase.
iv. Amylase digests starch and converts it to maltose, a
type of sugar.
v. The wave-like contractions of the oesophagusmuscles are known asperistalsis
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b. Stomach
i. in the stomach, food is mixed with gastric juices.
Gastric glands in the stomach wall.
ii. Gastric juices contains hydrochloric acid and
enzymes (rennin and pepsin) .
iii. The functions of hydrochloric acid include:
a. Hydrochloric acid stops the action of the enzymesin saliva.
b. It also kills bacteria in food.
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iv. Enzymes in the gastric juices start the digestion of
protein.
Example:
a. pepsin digests protein into peptones.
Protein pepsin peptones
b. Rennin coagulates milk in the stomach to help in
the enzymic action of pepsin.
Liquid milk proteins rennin solid milk proteins
v. Partially digested food is then released into the
duodenum.
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c. small intestine
i. The duodenum is the first parts of the small
intestine.
ii. The duodenum receives bile and pancreatic juice.
(bile is stored in the gall bladder)
iii. The function of bile:
a. Emulsifications of fat i.e. breaking up large fatty
globules into small droplets for enzymic action.b. Preparation of an alkaline medium for enzymic
action
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iv. The pancreatic amylase digests starch into maltose.
v. The protease digests protein/peptones into aminoacids.
vi. The lipase digests fat into fatty acid and glycerol.
vii. The small intestine (ileum) produces enzymeswhich digest maltose into glucose (simple sugar)
viii. Digestion is completed in the small intestine.
ix. The digested food is then ready to be absorbed
through the thin walls of the small intestine into the
bloodstream.
SUMMARY OF PROCESS OF CHEMICAL DIGESTION IN
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SUMMARY OF PROCESS OF CHEMICAL DIGESTION IN
THE HUMAN ALIMENTARY CANAL
Absorption of the products of digestion
1. Absorption is the process when the end products of
digestion enters the bloodstream through the small
intestinal walls.
2. The inner surface of the small intestine (6 metres
long) covered with millions of small projections about
1mm long. These projections are called villi @ villus.3. Food that has been digested into its most simple
form is absorbed by the villi @ villus on the small
intestinal walls into the bloodstream.
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4. The efficiency of absorption of digested food at the
small intestine can be increased by:
a. more villus to increase surface areab. villus with very thin walls
5. Each villus has a network of a blood capillaries and
a lacteal.6. Glucose, amino acids, minerals and water-solube
vitamins are absorbed into the blood capillaries.
7. Fatty acids, glycerol and fat-soluble vitamins
(vitamin A, D, E and K) are absorbed into the lacteal.
pg 52 figure 2.13
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struction:Write a task report based on these guideline
.Title:
.Aim:
.Hypothesis:
.Variables:
.Apparatus:
.Materials:
.Procedure
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a.Set up the apparatus as shown in the diagramb. Test the distilled water for starch and glucose at the beginning
of the experiment
c. After 30 minutes, test the distilled water again for the
presence of starch or glucose
d. Record your observation.
8.Observation and result:
9.Discussion:
10.Conclusion:
REABSORPTION OF WATER AND DEFECATION
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Reabsorption of water
1. The main function of large intestine is to reabsorb
water.2. The substances that enter the large intestine
consist of water and undigested food substances like
cellulose from the fibre of vegetables and fruits(roughage)
3. Water is reabsorbed from these undigested food
substances.
4. Undigested food materials together with water is
passed to the colon
(first part of the large intestine)rectum is the last
portion of the large intestine
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Defecation
1. Undigested food in the large intestine is expelled as
faeces through the process of defecation.2. When the rectum is full of faeces, the rectum
undergoes peristalsis and assisted by abdominal
contraction, will push the faeces through the anusto be expelled.
3. If an individual has problems passing motion, he or
she is said to be constipated.
4. Constipation takes place because of the lack of
water in the diet.
pg 53 figure 2.15
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HEALTHY EATING HABITS
1. Healthy eating habits will help maintain a healthy body.2. Unhealthy eating habits cause various health problems.
1. excessive nutrient health problems
Sugar tooth decay, obesity, diabetes
Salt high blood pressure, heart problems,
kidney damage
fat/oil heart problems, high blood pressure
2. lack of nutrient health problemsProtein kwashiorkor in children
Roughage Constipation
Vitamins lower immunity to diseases
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